Of same place



' (No Model.\

W. W. DEAN. V TELEPHONE EXCHANGE SYSTEM.

No. 597,052. I Patented Jan. 11, 1898 UNITED STATES PATENT Orrrcs.

IVILLIAM IV. DEAN, OF ST. LOUIS, MISSOURI, ASSIGNOR TO THE BELL TELEPHONE COMPANY OF MISSOURI, OF SAME PLACE.

TELEPHONE-EXCHANGE SYSTEM.

SPECIFICATION forming part of Letters Patent No. 597,052, dated January 1 1, 1898.

Application filed September 22, 1897. $eriel No. 652,5 3?. (No model.)

To all whom it may concern:

Be it known that I, WILLIAM XV. DEAN, a citizen of the United States, residing at St. Louis, in the State of Missouri, have invented a certain new and useful Improvement in Telephone-Exchange Systems, (Case No. 27,) of which the following is a full, clear, concise, and exact description, reference being bad to the accompanying drawing, forming a part of this specification.

My invention relates to telephone-exchange systems, and has for its object the improvement of systems employing automatic apparat us jointly controlled at the exchange and the subscribers stations for including the calling-generators in circuit with the signal-bells at the called-subscribers stations and removin g said generators from circuit with said bells and the removal of certain defects heretofore present in telephone-exchange systems employing clearing-out drops operated automatically by the apparatus at the called-subscribers stations.

As is well known, clearing-out signals in the more highly-perfected systems are operated automatically upon the movement of the automatic telephone switch-hooks at the subscribers stations. In some systems two clearing-out indicators are employed in each cordcircuit, one corresponding to and under the control of the calling subscriber, while the other corresponds to and is under the control of the called subscriber. In some cases it may be desirable to dispense with the clearing-out indicator corresponding to the calling subscriber, especially where automatic means are employed for signaling the called subscriber.

The called-subscribers clearing-out indicator in some systemsot the classes under dis cussion, for exampleis normally displayed, this normal position being maintained when the connecting-plug is inserted Within the called-subscribers spring-jack. "When the called subscriber responds, the displayed or indicating position of the clearing-out annunciator is changed and remains so while the telephone is off its hook. "When the called subscriber is through, the normal position of the clearingyout indicator is restored and the operator thereupon disconnects the sub It will be apparent in systems of scribers.

this class that extreme care will be required on the part of the operator to distinguish between the signal before the called subscriber responds and the same signal which is manifested when his receiver is replaced upon its hook.

One feature of my inventionhas for its object to obviate this ambiguity of signals. To this end I provide a called-subscribers clearing-out indicator governed by apparatus and circuit connections controlled at the called subscribers stations, the clearing-out indicator being adapted to maintain its normal idle condition upon the removal of the calledsubscribers receiver from its switch-hook. The switch-hook is adapted when the telephone-receiver is removed to place the clearing-out indicator in position to be operated upon the replacement of the receiver, so that but one signal is manifested, which signal is a positive clearing-out signal, and has but one meaning when displayed to the operator namely, to disconnect.

I Will explain my invention as applied to one type of telephone-exchange systems by referen cc to the accompanying drawing,which illustrates the preferred embodiment of the invention.

In the drawing I have illustrated three multiple switchboards 1, 2, and 3, to each of which subscribers A and B are connected. Line-jacks of well-known construction, provided with metallic thimbles and short and long line-springs, are shown, one jack at each board being connected with each subscribers line. The line-indicating apparatus a. b is well understood by those skilled in the art, and I do not therefore deem a description thereof to be essential.

I have shown a plug and cord circuit comprising an answering-plug cand aconnectingplug (1, the tips whereof are united by astrand e, including the helices of repeating coil 6', While the sleeves are united by a strand f, including the helices of repeating coil f, a centralized talking-battery g being bridged be tween repeating coils, as is well understood.

The operators outfit h is adapted to be included in a bridge of the cord strands by a key 72.. The clearing-out indicator 1' is adapted to be controlled by the calling subscriber, and

as the operation of the apparatus controlling the same is well understood I will not further mention'the same. 1

At each of the subscribers stations an automatic telephone-hook is normally grounded through a signal-bell 7c, in this instance preferably of high resistance. The switch-hooks are here shown as being connected with. the, long line-springs of the spring-jacks. The telephone-lines are normally discontinuous at the switch-hooks.

To make the further description of the apparatus clear, I will assume that A is the call ing subscriber, and B the called subscriber. At the central office I have illustrated'an apparatus for automatically transmitting signals to the called-subscribers stations having 'a calling or circuit-changing switch Z, which normally maintains the calling-generator m in connection with the strand f, whereby the called-subscribers bell is operated upon the insertion of the connecting-plug within the called-subscribers jack without the operation of the calling-switch. The helix of a magnetnis included in the cord strandf and is traversed by the current from the generator on, which current, however, owing to the high resistance of the signal-bell, is reduced sufficiently to prevent the operation of the armature n. W'hen the called subscriber removes his telephone from its hook the high resistance of bell It is replaced by the low-resistance ground connection g. The current from generator on is suliiciently increased to energize the magnet n enough to attract the armature n, whereby circuit is closed from ground n resistance a contact 0, helix of magnet 0, clearing-out indicator 1), preferably a small incandescent lamp, and the grounded battery q, connected. with the conductor q, uniting the metallic heels of the plugs. The magnet 0 attracts its armature which supports the calling-switch Z, thereby removing the generator from line. Switch Z when thus actuated makes contact with anvil 0 to complete the continuity of cord strand f.

It will be observed that when the plugs are first inserted in the spring-jacks the battery q is grounded through the line-indicating apparatus for the purpose of restoring and preventing the display of the line-indicators of the connected subscribers, as is well understood. To prevent the clearing-out indicator at this stage from being operated, I provide a resistance 8, which reduces the current in the path, including the clearing-out indicator and the heel of the connecting-plug, sufficiently to prevent the indicating-lamp from glowing.

IVhen the armatures n and that of magnet o are attracted, as stated, upon the removal of the called-subscribers telephone from its receiver a separate path from battery q is formed through the lamp 1) and the shunt about the same, including the contact 1*, helix of magnet 0, contact 0*, heel of plug d, the socket of the engaging springjack to the stead.

The contact 0 should be so adjusted that it engages the armature of magnet 0 before the generator-contact breaks engagement with switch Z. When the armature of magnet o is attracted and contact 0 is closed, the winding of magnet 0 then forms a low-resistance shunt about the resistance .9, permitting sufficient current to flow through the lamp 1) to light it if it were not for the shunt including resistance t and closed at 7' about said lamp.

When the called subscriber hangs up his telephone-receiver, the armature of magnet n will drop back and the shunt about the lamp 9 will be broken at r, the current from battery q thereupon following the low-resistance path about the resistance 8, the lamp through which the increased current now flows being thereupon caused to glow.

I prefer to employ a small incandescent lamp for the called-subscribers clearing-out indicator, but other automatically-operated clearing-out indicators may be employed in- It is apparent that'the lamp is extinguished when the subscribers are disconnected, so that the lamp is automatically restored'to its normal condition, being thus a self-restoring indicator.

It will be observed that in this system I' have provided means controlled by the switchhook at the calledsubscribers station governing the clearing-out signal. The operative condition of this means is only partially changed when the receiver is removed from its h'ook, so that no signal is at this stage presented, the telephone-hook being adapted to complete the change of the operative condition of said means when it is actuated upon the replacement of the receiver, so at this point a definite signal is presented. Thus it takes two motions of the switch-hooknamely, the elevation and depression thereofto effect the clearing-out signal. In other words, I have provided a clearing-out signal which requires the two motions of the switchhook referred to to operate the same.

I have herein shown and described the preferred embodiment of my invention and one type of apparatus for practicing the same; but it is obvious that changes may readily be made without departing from the spirit of my invention; and I do not, therefore, wish to be limited to the precise system and apparatus herein shown and described; but,

Having thus described my invention, what I claim as new, and desire to secure by Letters Patent, is

l. Ina telephone-exchange system, the combination with two telephone-lines, of switching apparatus at the exchange for uniting said lines for conversation, a signal-receiver at one of said stations, a signaling-generator for operating the same, a switch-hook at the latter station for the receiver adapted to occupy one position through the influence of the receiver when supported thereon and an alternative posit-ion when the receiver is removed, an automatically-operated clearingout indicator at the exchange adapted to be associated with the called-subscribers line by said switching apparatus, a circuit including or adapted to include said clearing-out indicator, and means for changing the condition of said circuit to cause the clearing-out indicator to present a signal, the switch-hook being adapted to control said means and partially to effect an operative change in the condition thereof when actuated upon the removal of the telephone, said switch-hook bein g furtheradapted to complete the operative change in the condition of said means when restored to its normal position through the influence of the receiver when replaced thereupon, whereby the condition of the clearingout-indicator circuit is changed to operate the clearing-out indicator, substantially as described.

2. In a telephone-exchange system, the combination with two telephone-lines united at the central oflice, of a signal-receiver at one of said stations, a signaling-generator for operating the same, a switclrhook at the latter station for the receiver adapted to occupy one position through the influence of the receiver when supported thereon and an alternative position when the receiver is removed, an automatically-operated signal apparatus at the exchange adapted when operated to present and maintain a signal, and suitable circuit connection between the signal apparatus and the calledsubscribers line and switch-hook, said switch-hook being adapted when operated upon the removal of the telephone partially to eliiect an operative change in the condition of said signal apparatus and to complete the operative change when actu' ated upon the replacement of the telephone, whereby a clearing-out signal is presented substantially as described.

3. Inatelephone-exchangesystem,thecombination with two telephone-lines extending from subscribers stations and united at the central oiiice, of a signal-receiver at one of said stations, a signalinggenerator for operating the same, a switch at the latter station, an automatically-operated signal apparatus at the exchange adapted when operated to present and maintain a signal, and suitable circuit connection between the signal apparatus and the called subscribers line and said switch, said switch being adapted upon one movement thereof partially to effect an operative change in the condition of said signal apparatus and to complete the operative change upon its second actuation or movement, whereby a clearing-out signal is presented, substantially as described.

4. In a telephoneexchange system,the combination with two telephone-lines extending from subscribers stations to the exchange, of

a cord-circuit for uniting and disconnecting said lines, a signal-receiver at one of said stations, a signaling-generator, a switch-hook at puit and thereby with said switch-hook and the called-subscribers line, a source of current connected or adapted to be connected with said clearing-out indicator, said switchhook being adapted when operated upon the removal of the telephone partially to effect an operative change in the condition of the circuit connection of the clearing-out indicator, and to complete the operative change when actuated upon the replacement of the telephone whereby a clearing-out signal is presented, substantially as described.

5. In a telephone-exchan ge system the combination with two telephone-lines extending from subscribers stations to the exchange, of a cordcircuit for uniting and disconnecting the lines, a signal-receiver at one of said stations, a signaling-generator for operating the same, a switch at the latter station having two alternative positions, a clearing-out indicator, an electroinagnet at the exchange, paths of high and low resistance, said switch being adapted when occupying one position to include the magnet in the path of high resistance, and when actuated to its alternative position serving to include said magnet in the path of low resistance which is thereupon operated, a circuit including a battery, means operated by said magnet for closing said circuit through said clearing-out indicator, means for maintaining the circuit closed, a shunt-circuit which is closed about said clearing-out indicator by said electromagnet when operated to prevent the operation of said in dicator, said switch at the called station being adapted when restored to its normal position to reinclude said magnet in the path of high resistance, whereby the armature thereof is released and the clearing-out indicator operated, substantially as described.

6. In atelephone-exchangc system,the combination with two telephonedines extending from subscribers stations to the exchange, of a cord-connecting apparatus for uniting and disconnecting said lines, a signal-receiver at one of said stations, a signaling-generator for operating the same, a switch at the latter staing a battery, a circuit-changing switch, a second electromagnet for operating the same, said switch when operated serving to close said circuit through the clearing-out indicator, the first aforesaid magnet being adapted to close circuit through the second electromagnet to operate the same, the second electromagnet being adapted to close circuit through itself when operated, whereby the circuit-changing switch controlled thereby is maintained in the position to which it has been actuated, a shunt-circuit which is closed about the clearing-out indicator by the first aforesaid electromagnet when operated to prevent the operation of said indicator, said switch at the called station being adapted when restored to its normal position to reinclude the first aforesaid magnet in the path of high resistance, whereby the armature thereof is released, the shunt-circuit being thereupon broken and the clearing-out indicator operated,and switch-contacts controlled by the cord-connecting apparatus included in the circuit closed by the second electromagnet through itself, said switch-contacts being separated upon the manipulation of the cord-connecting apparatus in disconnecting the telephone-lines, substantially as described.

7. In atelephone-exchange system,the combination with two telephone-lines extending from subscribers stations and united at the exchange, of switching apparatus for uniting and disconnecting said lines, a signal-receiver at one of said stations, a signaling-generator for operating the same, a signalingapparatus adapted to present and maintain a clearing-out signal at the exchange, suitable circuit connection between the signaling apparatus and the called-subscribers line, a switch-lever adapted to change the circuit condition and the operative condition of said signaling apparatus to give a.clearing-out signal, means for preventing said signaling apparatus from presenting a clearing out signal with the switch-lever unchanged from its normal idle position, said switch-lever ;n being moved from and restored to its normal position being adapted to effect an operative change in the condition of said signaling apparatus to present a clearing-out signal, substantially as described.

8. The combination with a telephone-line extending from a subscribers station to the central office, a switch-hook for the receiver, a signal-receiver of high resistance at the subscribers station, a signaling-generator, a callingswitch adapted in its normal idle position to connect the generator in circuit with said signal receiver, an electromagnet included in the circuit containing the signaling-generator and the signal-receiver, a path of low resistance which is adapted to be closed through the said electromagnet by said switch-hook when actuated to its alternative position upon the removal of the receiver, said electromagnet being thereupon operated, a second electromagnet operated by the first electromagnet to actuate said calling-switch to disconnect the generator from line, a second circuit which is adapted to be closed by the electrom agnet through the winding thereof when said magnet is operated, whereby the calling-switch is maintained in the position to which it has been actuated, a cordcircuit, a connecting-plug for connecting the cord-circuit with said telephone-line, and contacts in eluded in the aforesaid second circuit controlled by said connecting-plug which is adapted to separate the same when manipulated to disconnect the cord-circuit from said line, substantially as described.

In witness whereof I hereunto subscribe m y name this 17th day of September, A. D. 1897.

XVILLIAM XV. DEAX.

\Vitnesses:

7M. ll. \VHITE, FREDERICK J. RANLETT. 

